The present invention relates to a device which can take flat units from a stack, one unit at a time. Such devices find practical use in connection with systems where a sheet of paper is to be put into an envelope. Usually, the sheets of paper are stacked in a unit and placed in a holding device. From this holding device the sheets are conveyed in one way or other to the envelope, where they are inserted by machine. This insertion is desired to be performed as quickly and as safely as possible.
An object of the present invention is to provide apparatus to take sheets of paper from a stack as fast as possible, one sheet at a time, and to insert this sheet into an envelope. This is performed by means of the present invention by placing a stack of sheets on two supports which are placed next to each other. The two supports are parallel with each other and they lie true against two opposite edges of the bottom sheet. One of the supports is stationary, but it can be adjusted into various positions. The other support can rotate and it has a part which can suck the edge of the bottom sheet which lies true against the support, and when the sheet has been sucked it will be carried on to a conveyor belt. When the sheet is carried on to the conveyor belt the speed of the sheet can be increased so that the sheet has the same speed as the conveyor belt when it reaches the belt.
According to the present invention it is suitable for the other support to have the shape of three rollers situated next to each other and with the same axis of rotation. The two outer rollers can rotate at a constant speed, whereas the intermediate roller rotates intermittently and is equipped with suction devices so that the roller regularly sucks sheets of paper which lie true against the support. This roller is primarily arranged in such a way that it will rotate part of one revolution, primarily one quarter of a revolution or part of a revolution at a time. Between every part of a revolution or quarter of a revolution is an interval so that a sheet which is fed further on by the roller has left the stack before the next sheet is sucked so that it lies true against the roller. The sheet will best lie true against the roller when this is mainly stationary. The interval can be obtained by means of, for instance, a coupling containing a wheel with radial tracks, such as a Maltese cross. Such a coupling is described in the book called "Handbok i Finmekanik" (Handbook of Precision Mechanics) page 426, which book has been revised by Bartil Ejerhed.
According to the invention it is suitable for the intermediate roller to have a hollow shaft which is connected with a suction unit, for instance a vacuum pump, and in the shaft are provided a number of holes which are placed axially next to each other and which serve as suction openings. On the surrounding, intermediate roller can be arranged corresponding holes in its periphery to cooperate with the holes in the hollow shaft. In this way, the intermediate roller when rotating and passing the holes of the hollow shaft is going to have an increasing suction capacity, which reaches a maximum and then decreases depending upon the rotation of the roller.
According to the invention, the rollers described can be replaced by a number of wheels which have the same function as the rollers.